@primrosea
No, if I was in another country with foreign foods I would just eat what I liked from the local cuisine. No wheat? I'll have rice. No rice? I'll have naan. No naan? I'll have pasta. No pasta? I'll have potatoes. Etc.
Plus there's this ridiculousness of how everyone always loves every introduced Japanese food, whether it's sushi, soy sauce, mayo, pudding, etc, when a lot of these tastes are acquired, and generally requires specialized knowledge and equipment (like the ability to properly flash-freeze fish to kill parasites before serving it as sushi, or the proper way to make sushi rice, which requires rice vinegar, which is made by fermenting rice using a specific type of yeast that likely doesn't exist in an alternative world (of course, neither would specific varieties of fruits, grains, vegetables and animals also exist, meaning really an isekai'd person shouldn't know how to cook much of anything)).
So good luck, isekai guy, on finding Aspergillus mold (oh, and the fermentation/aging process takes 5 to 8 months, and don't forget the pasteurization process that I'm totally sure you also know how to do.)
Not to mention that the number of Japanese students or officeworkers who actually know how to make these products from scratch (like soy sauce) that will actually taste good is likely nonexistent. (At least this manga showed it was just an experiment, but watch, everyone will love it).
Cooking is science, and science depends on physics, which are not going to necessarily be the same. Elevation, humidity, ambient temperature, fluctuations in cooking temperature due to primitive ovens, etc - and suddenly your cooking or baking results might be totally different. You go to the grocery store, and every single fruit or veggie you buy is something that has been selectively grown through genetic manipulation by people with decades of experience, and much of it is only available to you as a fresh ingredient because of interstate highways, international shipping and the gasoline engine. And here we are in isekai societies that haven't even invented processes like canning or bottling and rarely seem to even have refrigeration (or electricity).
These people would only be eating what could be grown locally, perhaps within about 100 miles. Anything else would be exorbitantly expensive or totally unavailable.